Heat transfer apparatus for granular material



March 1, 1955 A. L. COOPER 2,

HEAT TRANSFER APPARATUS FORIGRANULAR MATERIAL Failed May 31. 1951 sShe'efcs-Sheet 1 Clttornegs March 1, 1955 A. COOPER u 2,703,225

HEAT TRANSFER APPARATUS FOR GRANULAR MATERIAL Filed May 31, 1951 3Sheets-Sheet 2 Zhwentor ALBERT L. COOPER (Ittornegs March 1, 1955 A. L.COOPER HEAT TRANSFER APPARATUS FOR GRANULAR MATERIAL Filed May 31, 19513 Sheets-Sheet 3 Snuentor ALBERT L COOPER attorney United States PatentHEAT TRANSFER APPARATUS FOR GRANULAR MATERIAL Albert L. Cooper, ColoradoSprings, Colo., assignor to Holly Sugar Corporation, Colorado Springs,Colo., a corporation of New York Application May 31, 1951, Serial No.229,238

6 Claims. Cl. 257-228) This invention relates to heat transfer apparatusfor granular material, and more particularly to apparatus for coolinggranular material such as sugar.

In the production of a granular material such as sugar, which iscrystallized from solution and separated in centrifugal separators,being washed with clear water during such centrifugal separation, it iscustomary to heat the sugar, as in a dryer, to drive off moisture, andthen separate the sugar granules in accordance with size. If packedimmediately in bags or sacks containing relatively small quantities, theheat contained in the sugar does not unduly complicate the problemsinvolved, but immediate packing into bags requires a relatively largelabor force, thus adding considerably to the cost of operation of asugar factory, since the sugar is produced over a period of perhaps onlya few months, whereas it is sold or distributed throughout the entireyear. However, cooled sugar does provide better scale operation and moreaccurate weights, and reduced heat results in longer life of papercontainers. More recently, it has become the practice to store the sugarin huge bins or towers, but if the sugar is placed in the towersimmediately after drying, the heat in the sugar produces a number ofdifliculties. Warm sugar stored in large bulk bins tends to causeresidual surface moisture to migrate to cooler zones, as in the lowerportion of the bin, thus producing caking or hard cores. When cakes orcores of considerable extent occur, about the only manner in which thesugar can be handled is to redissolve the sugar in hot water, andrecrystallize. This, of course, involves a comparatively large expense,since it is one of the principal operations of the sugar factory, andwhen it is necessary for the same sugar to go through crystallizationtwice, the second crystallization cost is a loss.

Additional difficulty is introduced by the fact that the production rateof sugar in a sugar factory or refinery is not uniform at all times.That is, when a white pan, for instance, is struck or discharged, thecentrifugal separators are in operation continuously for a period oftime, until all the sugar from that pan has passed therethrough. Thismeans that the production is periodic, and while dryers generally havesuflicient capacity and are effective over a comparatively large loadrange, a cooler for the sugar must be able to handle the production ofthe heated sugar as it comes from the dryer, i. e. a relatively largeflow for a period of time, then a smaller flow, dwindling perhaps to anextremely low rate or perhaps nothing before the next white pan isstruck or discharged.

Because of its granular nature, it is difficult to cool effectively anylarge amount of sugar, since heat transfer through the sugar isrelatively slow. Also, uniformity of coolingthat is, the cooling of eachsmall part of a relatively large mass of sugar to the sametemperature-is diflicult.

Among the objects of this invention are to provide a novel heat transferapparatus for granular material; to provide such apparatus which isparticularly adapted for the cooling of sugar; to provide such apparatuswhich may be constructed to have a comparatively large capacity; toprovide such apparatus which tends to cool each part of a relativelylarge mass of granular material to a substantially uniform temperature;to provide such apparatus which can produce uniform cooling,irrespective of whether the amount of sugar passing therethrough issmall or large, up to its ultimate capacity; to provide such apparatuswhich is adapted to handle granular material in amounts which changeperiodically, and particularly in amounts which periodically reach amaximum and then diminish to a minimum of little or no material, such asfollowing a strike of a sugar pan; to provide such apparatus whichrequires a comparative minimum of attention; and to provide suchapparatus which is effective and efiicient in operation.

Additional objects and the novel features of this invention will becomeapparent from the following description, tallierli1 in connection withthe accompanying drawings, in w 1c Fig. 1 is a side elevation, brokenaway at the center, of a sugar cooler embodying the principles of heattransfer apparatus for granular material of this invention;

Fig. 2 is an enlarged vertical section, broken away at the center, of aheat transfer tube forming a part of the sugar cooler of Fig. 1;

Fig. 3 is a vertical section, on a slightly larger scale than Fig. 1,taken along line 3-3 of Fig. l, and also broken away at the center;

Fig. 4 is a partial horizontal section, taken along line 4 4 of Fig. 1,on a slightly larger scale than Fig. 1;

Fig. 5 is a horizontal section taken along line 5-5 of Fig. 1, on aslightly larger scale than Fig. 1;

Fig. 6 is a further enlarged fragmentary vertical section taken alongline 6-6 of Fig. 5;

Fig. 7 is a fragmentary horizontal section taken along line 77 of Fig.6; and

Fig. 8 is a diagram of an installation of the sugar cooler of Fig. 1 ina sugar factory.

Heat transfer apparatus for granular material, constructed in accordancewith this invention, may be embodied in a sugar cooler which, as in Fig.1, may comprise a generally cylindrical shell S disposed in verticalposition and closed at its lower end by an inverted, generally conicaloutlet housing 0, and closed at its upper end by an inlet housing I. Aseries of relatively long, vertically extending heat transfer tubes Tare enclosed within shell S, and each tube T is constructed individuallyto provide an adequate transfer of heat from the sugar to be cooled. Aheat transfer liquid, such as water for cooling purposes, may beintroduced into the lower end of the shell S through a water inletmanifold 10, and discharged from the upper end of the shell through awater outlet manifold 11. In passing from the lower to the upper end ofthe shell S, the water not only circulates around each of the tubes T,but also through the tubes, but without contacting the sugar, as will beexplained below.

As in Fig. 2, each of the tubes T is provided with an inner tube 12,which forms an annular sugar cooling space within the tube T and aroundthe inner tube 12, an inlet connection 13 for each tube 12 extendingbetween the inner tube 12 at its lower end and the tube T at a circularopening provided for the purpose, to each of which the inlet connection13 may be welded, brazed or otherwise attached. A similar outletconnection 14 may be attached at one end to the inner tube 12 and at itsopposite end to the tube T at an opening provided for the purpose, againas by welding, brazing or the like. The inlet and outlet connections 13and 14 for the inner tubes 12 are disposed at points relatively close tothe lower and upper ends, respectively, of the tubes T, it beingunderstood that most of the tube T of Fig. 2 is included in the portionbroken away in the center, since the tube T, for instance, may have adiameter of 3 inches and a length of 30 feet. As in Fig. 3, the lowerends of the tubes T are attached and sealed, as by rolling, to a lowertube sheet 15, which is provided with spaced holes corresponding to thelocation of the tubes, against which the tubes may be expanded, whilethe upper ends of the tubes T are similarly attached and sealed to anupper tube sheet 16 by expanding. The tube sheets 15 and 16 may extendlaterally beyond the shell S, to form flanges for attachment of theoutlet housing 0 and inlet housing I, respectively, as througha flange17 of housing 0 and a flange 17' of housing I, while the ends of shell Smay be attached to tube sheets 15 and 16 in a suitable manner, as bywelding. The cooling water is fed into the lower end of the shell S,from the box-like, water inlet manifold 10, through a series of spacedopenings 18 in the shell S, as in Figs. 1 and 3, while the water may bedischarged at the upper end of the shell through a series of similaropenings 19 into the box-like, water outlet manifold 11. As will beevident, the cooling water will tend to fill the space within shell Scompletely, except for the sugar cooling space between tubes T and tubes12, the water flowing upwardly around the tubes T and also through theinner tubes 12.

The annular space, or ring thickness, between each inner tube 12 andtube T is preferably sufficiently narrow that an adequate transfer ofheat to all portions of the sugar passing downwardly through each tube Twill be produced, and so that all of the sugar will be cooled tosubstantially the same temperature by the time the sugar reaches thebottom of each tube T. Preferably, sufiicient water is passed throughthe shell S so that the rise in temperature is on the order of a fewdegrees or a fraction of a degree only, whereas the sugar itself may becooled over a much wider range of temperature, such as from 55 C. downto about 30 C. Thus, for an outside diameter of tubes T of 3 inches andan inside diameter of 2 inches, the inner tubes 12 may have an outsidediameter of 1 inches, or approximately half the diameter of the tube T.With such dimensions, the ring thickness of the annular space betweenthe tubes will be 1 inches, and this is generally sufiicient toaccommodate granular sugar, since there will ordinarily be no lumpsgreater than ,6, inch in diameter. For uniform cooling it is desirablethat the sugar fiow evenly and without interruption through each tube T.Also, if the fiow can be controlled so that each tube T remains full ofsugar while in operation, the rate at which sugar is discharged from thelower end of each tube T will determine not only the amount of sugarflowing through the tube but also the rate at which it flows. Forcontrolling the flow of sugar through each tube, i. e. to provide meansat the lower end of each tube for controlling the flow of granularmaterial therethrough, any suitable individualized control device may beused, but a preferred control means consists of an inverted cone havinga diameter at its upper end larger than the tube T, as in Fig. 2, andconveniently attached to the tube sheet 15. although the cone 20 may beformed by or attached to the lower end of a tube T. The included anglebetween the sides of the inverted cone 20 is preferably such that thesides of the cone slope at an angle greater than the angle of repose ofthe sugar. An included angle of 60 is convenient for use, since thesides of the cone will be disposed at 60 to the horizontal, i. e. at anangle considerably greater than the angle of repose of mill run sugar ofapproximately 33. In addition, the lower end of the inverted cone 20 isprovided with an orifice 21 having a diameter D, the orifice preferablybeing reamed or otherwise accurately dimensioned, to a size which willpermit the sugar to be discharged from the lower end of the tube T at arate which will produce the desired retention time or rate of flow ofthe sugar down through the tube. The diameter D at the orifice 21preferably has a size such that the cross sectional area of the orifice21 is less than the cross sectional area of the annular splace betweenthe outside of tube 12 and the inside of tu e T.

The cross sectional area of the discharge opening 22 of the invertedconical outlet 0, as in Fig. 3, is preferably greater than the combinedcross sectional area of the orifices 21, so that when the cooler isoperating at .full capacity, the flow through the discharge opening 22can be as reat or greater than the flow from all of the control orifices21. The cross sectional area of the inlet opening 23 of the inlethousing I may, of course, be any desired value sufficient to accommodatethe maximum flow into the cooler, being generally greater than the areaof outlet opening 22, and equal to or slightly greater than the area ofthe inlet tube or pine 24 leading thereto.

In further accordance with this invention, an inlet plate 25,constructed so that it is self-cleaning, is preferably mounted on theupper tube sheet 16, and provided with surfaces which are inclined withrespect to the horizontal at an angle greater than the angle of reposeof the sugar, or other granular material being cooled or to or fromwhich heat is transferred. Again, an angle of 60 is convenient, since itis considerably greater than the angle of repose of mill run sugar ofapproximately 33. Thus, the inlet plate is provided with a series ofapertures or orifices, corresponding in diameter to the tubes T, buthaving angularly inclined sides, such as at an angle of 60 to thehorizontal. Also, the plate 25 is sufiiciently thick that the ridgesbetween the tubes T will be pointed, as

will be evident also from Fig. 2. The inlet plate 25 may be made ofplastic or similar material readily formed or machined, since there isno great stress thereon.

During operation of the cooler, whenever a white pan, for instance, isstruck, and the granulated sugar begins to be delivered from the dryerto the cooler, a valve 26, as in Fig. 1, such as a butterfly valve andinstalled in the outlet pipe 27 leading from the lower end of outlethousing 0, is preferably closed, so that sugar will build up in theoutlet 0, and then build up in the tubes T. When the tubes T becomefilled with sugar, a pile 28 of sugar will then begin to build up toinlet plate 25, as in Fig. 3. When this pile 28 reaches a predeterminedheight, corresponding to the probable or average maximum flow of sugarfrom the pan involved, or to all of the tubes T being full, the valve 26may be opened. This insures that the tubes T necessary for the operationwill be full before discharge is started. The level of sugar in theinlet housing I, such as defined by the pile 28, may be observed througha transparent window 29 of Fig. l, or a telegauge or other level device,such as a Bin-Dicator, may be installed within the inlet housing I, andthe valve 26 opened automatically when the pile reaches a predeterminedheight. Assuming that all or less than the total number of tubes T arefull, when the sugar discharge valve 26 is opened, the level of sugar inthe outlet 0 will drop, until the flow through the valve 26 correspondsto the amount of sugar being discharged through the tubes in use. Ofcourse, the discharge orifices 21 will determine the rate of flow of thesugar through the tubes T. If the flow of sugar through the inlet pipe24 should decrease, it will be evident that the pile 28 will tend todecrease in size, so that the tubes around the edges of the pile willbegin to be uncovered. However, whenever a tube T is uncovered, thesugar will merely flow downwardly therethrough, at a rate determined bythe discharge orifice 21 at its lower end, until the tube is empty.Thus, as the amount of sugar from the dryer, previously received fromthe centrifgugals, decreases during a strike, there will be a smallernumber of tubes T in operation. However, the flow through each of thetubes T in service will be the same, so that all of the sugar will tendto be cooled to the same temperature.

Furthermore, if the amount of sugar tends to increase, the pile 28 willincrease in size, whereupon additional tubes T will begin to receivesugar, and these will tend to become full, since the fiow at the lowerend is restricted by the discharge orifice 21, so that the time ofpassage of this sugar down the tubes T will tend to become the same asthrough the tubes more centrally located with respect to pile 28. Ingeneral, however, during a strike, the flow of sugar will tend toincrease rather quickly to a maximum, and perhaps level off for sometime, and then taper off while the strike is being finished. After thestrike is finished, valve 26 may be closed for the next strike, and theoperation repeated.

When a telegauge, Bin-Dicator, or other automatic device is utilized toindicate or measure the height or extent of the pile 28 of sugar at thebeginning of the strike, the outlet valve 26 may be solenoid or fiuidoperated, so that it may be closed manually prior to a strike, as byremote control, and will be automatically opened after the sugar in theinlet housing I has reached a predetermined level or pile size. In suchcase, the level indicator may be electrically connected to a solenoidwhich opens an air valve controlling the release of air pressure on acylinder or the like holding the valve 26 closed, and the indicator maybe reset manually to cause the valve 26 to close automatically, afterone strike and prior to the next. In addition, an orifice 30, such ashaving a 60 approach section, may be installed in a vertical section ofoutlet pipe 27 below valve 26, as in Fig. l, in the event that a suddenflow of sugar from outlet housing 0, at the time valve 26 is opened, maytend to cause overloading or clogging of subsequent equipment, such aselevators, conveyors, separators, and the like. It will be understood,of course. that when the flow of granular material to the heat transferapparatus of this invention is substantially continuous and does notconsist of periodically heavy loads, the inlet plate 25 will accommodatevariations in flow, and that the control of the valve 26, as describedabove, may be unnecessary.

As shown in Figs. 4 and 5, a hexagonal arrangement of the tubes has beenfound to be convenient, particularly for design purposes, since the flowand distribution of water through the tubes T may bemade on the basis ofsix similar triangular arrangements. Thus, the ninetyone tubes shown inFigs. 4 and 5 may be disposed in six similar triangular arrangements offifteen tubes each, with one tube in the exact center. The inlet housingI, as in Figs. 1 and 4, may be provided with side walls 32 disposed inhexagonal relationship, and the flange 17 therefor provided with ahexagonal aperture into which the sides 32 extend for attachment to theflange, as by Welding. The inlet plate 25 thus may be hexagonal and maybe provided with straight edges, thereby avoiding a shelf formed by thesegments around the edges of the hexagonal configuration of the tubes onwhich sugar might tend to remain. For uniform flow of heat transferfluid, each of the inlet connections 13 and outlet connections 14 of theinner tubes 12 face outwardly, with the openings of all tubes of eachtriangular arrangement facing in the same direction and the center tubein any desireddirection, and, as in Fig. 5, the water inlet openings 18may be so spaced that there is no opening immediately in front of a tubeT nearest the shell S. As shown in Figs. 1 and 6, the flow of waterthrough the space within shell S may be controlled by suitable bafflemeans for directing the flow of liquid through the inner tubes 12 aswell as around the tubes T. Thus, the flow of water around the tubes Tmay be restricted by horizontal bafile plates 33, which may be placed invertically spaced relation from the lower to the upper end of the shellS, such as in the positions indicated in Fig. 1, and correspondingpositions over the remainder of the shell. For example, when the tubes Tare approximately 30 feet in length, the baffle plates 33 may be spacedabout 2 feet apart and may be attached at their edges to the inside ofthe shell, as by welding, either continuous or spot. Each baflie plate33 is provided with a series of holes 34, as in Figs. 6 and 7, throughwhich the tubes T extend and whichform around each tube T an annularspace which preferably has a cross sectional area slightly less than thecross sectional area of the tube 12 inside the tube T. Thus, for 1 /2inch 0. D., 16 gage, inner tubes 12, each hole 34 may leave an annularspace having a ring thickness of approximately inch around a 3 inch 0.D. tube T, or a cross sectional area of approximately 0.911 sq. inch, incomparison to approximately 1.486 sq. inches for the inner tube 12. Aswill be evident, the incoming water is forced to flow, by the lowermostbaffle 33, into the inlet openings of the inner tubes 12, and also intothe center of the nest of tubes. The additional bafiles produceturbulence and mixing of the coolant, thus preventing hot spots, andalso retard the upward flow sufficiently so that an adequate rate offiow through the inner tubes 12 is assured.

The inner tubes 12 may also be maintained in position within the tubesT, as in Fig. 7, by outwardly extending spacing rods 35 welded orotherwise secured to the inner tubes 12, in units of three rods spaced120 apart around the tube 12, which may in turn be spaced any desireddistance apart vertically of the tubes 12, such as approximately 5 feet.The rods 35 do not require a precision fit, but the ends may be machinedor rough ground merely within reasonably accurate'dimensions, such as towithin approximately 1 inch of the distance to the inner surface of thetube T.

The water inlet manifold 10 may be provided with two inlets 37, as inFig. 5, and the water outlet manifold 11 may be similarly provided withtwo outlets 38, as in Fig. 1, the same being diametrically opposed ineach instance, to insure a more uniform distribution and supply of thewater to the interior of the shell S. As in Fig. 5, the water opening 18opposite each inlet 37 may be omitted, to prevent a direct flow of waterfrom the inlet straight into the adjacent tubes and produce a moreuniform distribution of the water, while a similar provision may be madein the case of the upper water openings 19. The water circulated throughthe cooler may be natural water sufiiciently cool to accomplish thedesired cooling, or may be artificially cooled, as by means of a spraypond or refrigeration, when necessary. As indicated previously, acomparatively large amount of water preferably is passed through thecooler, so that the rise in temperature of the water between the inletand the outlet is not great. When the supply water'is at a lowertemperature than necessary, a portion of the water may be recirculatedthrough the cooler, as by an automatically operating, temperatureresponsive regulat ing valve. The pressure of the water supply to thecooler inlet need not be great, but only sufficient to force the waterup through the cooler to the outlet, as for a distance of 30 feet, sincethe water may be permitted to flow with only slight pressure into theoutlet manifold 11 from the shell S.

The diameter D of each tube orifice 21 may be proportioned in accordancewith the length and the cross sectional area of the annulus within tubeT, around the inner tube 12, correlated with the retention time desired.These factors may, of course, vary for different materials, but for millrun granulated sugar to be cooled, for instance, from an averagetemperature of 55 C. to 29 C., each tube T may be a 3 inch 0. D., 16gage tube, and each tube 12 a 1%. inch 0. D., 16 gage tube, with thetube T being approximately 30 feet long and the inlet connection 13 andoutlet connection 14 each being spaced at a center line 6 inches fromthe lower and upper end of the tube T, respectively. In tests, the flowof mill run sugar was found to be 9.72 lbs. per minute, or approximately10 lbs. per minute or 0.3 tons per hour, when thediameter D of the coneorifice 21 was 0.8 inches. For a tube unit having the same dimensions asgiven above, except that the length of the tube T was only 20 feetinstead of 30 feet, it was found that the amount of sugar contained inthe tube was approximately 32.85 lbs., and the retention time wasapproximately 972 3.37 minutes for an average temperature drop of thesugar from 55.2 C. to 35.5 C. and an average rise in the cooling watertemperature from 14.6 C. to 15.1 C. Thus, for a tube 30 feet long, itwould be expected that the sugar contained in each tube would beapproximately 49.2 lbs. and that the retention time would be 5 minutes,for a temperature drop of 55 C. to 29 C. for the sugar and a coolingwater temperature rise from 13 C. to 14 C. The diameter D, shown in Fig.2, of the flow control orifice for the tube T may vary in accordancewith the rate of flow desired, and in turn be affected by the type ofmaterial being cooled. However, on tests on mill run sugar, thefollowing results were secured, which will provide a basis for theselection of a desired orifice diameter for any desired rate of flow ormaterial, it being understood that the axis must be vertical and theangle included between the sides of the cone above the orifice was 60,and that a variation in this angle will affect the rate of flow throughthe orifice.

Flow, pounds Diameter of orifice, inches per minute Flow, tons per hourFrom the above results, some of which are extrapolated, the followingformula was deduced:

F=Flow in lbs. sugar per minute K=18.13 (constant for granulated sugar)D=Diameter of orifice in inches.

maximum capacity of a cooler having ninety-one tubes, as illustrated,when an 0.8 inch diameter orifice below a 60 cone is installed beloweach tube, would be 91 9.72=874.52' lbs. per minute, or 29.1 tons perhour, and assuming that the six tubes at the points of the hex would notbe filled, so that only 85 tubes were in operation, the maximum ratedcapacity would be or, to be conservative, approximately 25 tons perhour.

A sugar cooler constructed in accordance with this invention may beinstalled in a sugar factory in a manner similar to that illustrated inFig. 8, wherein sugar is delivered from a dryer (not shown), as througha scroll conveyor, to the lower end of an elevator 40, transported tothe upper end of the elevator 40 and discharged through pipe 24 into theinlet I of the cooler. After downward passage through the tubes T withinthe shell S, the cooled sugar may be discharged through pipe 27 to thelower end of a cooled sugar elevator 41, and discharged from the upperend thereof through a pipe 42 to a horizontal scroll conveyor 43, whichfeeds the cooled sugar into one or more separators 44, such as two, asshown. Separators 44 classify the sugar into sizes or grades, such asfine, bakers or superfine, and scalpings, and preferably discharge intotemporary or permanent storage bins or the like.

The material of which the various parts of the heat transfer apparatusof this invention are made may vary considerably, although certainmaterials may be preferred where available and also economicallyfeasible. The shell S, of course, may be made of sheet or plate steel,while the inlet and outlet water manifolds may be made of similarmaterial, as by an upper and lower flat ring welded to the outside ofthe shell S and to an outer annular ring, to form a box-like structure.The tubes T, and also inner tubes 12 and their inlet and outletconnections, are made of material which will not rust, have no harmfuleffect on the sugar, and have a comparatively high coeflicient of heattransmission. Brass or other copper containing metal are preferredmaterials, although other materials, such as stainless steel oraluminum, may be used when the preferred materials are not available.The orifice cones 20 and the inlet and outlet housings may be made ofthe same or similar material, or of galvanized steel. The inlet plate25, as indicated previously, may be made of plastic, such as a syntheticresin, while the baffle plates 33 may be made of mild steel. The tubesheets 15 and 16, which also provide flanges for the shell S, may bemade of stainless clad steel, with the stainless layer facing the inletand outlet housings, respectively, and the shell S welded to the mildsteel side. The outlet housing and inlet housing I may be made ofgalvanized steel plate, or of brass or stainless steel if desired, andas indicated previously, may be welded to the flanges 17 and 17,respectively. It will be understood, of course, that other materials maybe found suitable, and utilized when desired, as well as other methodsof constructing the parts and assembling or attaching them together.

From the foregoing, it will be evident that the heat transfer apparatusfor granular material of this invention, fulfills to a marked degree therequirements and objects hereinbefore set forth. As will be evident,such apparatus is particularly adapted for the cooling of sugar,although it may be utilized for the cooling or heating of other granularmaterial. As will also be evident, the apparatus has a comparativelylarge capacity, but can produce uniform cooling, irrespective of theamount of material passing therethrough, by virtue of the controlledrestrictive flow through each tube, which insures that the material willremain in each tube for a period of time sufiicient to cool the same thedesired amount. Thus, the individual flow control means at the lower endof each heat exchange tube will restrict the downward descent ofgranular material in each tube to less than free flow, so that granularmaterial is adequately maintained in contact with the heat exchangetubes during descent. As will be further evident, each tube in operationproduces substantially the same amount of cooling for the materialpassing therethrough, due to the uniform flow, and therefore each partof a relatively large mass of granular material may be cooled to asubstantially uniform temperature. As will be additionally evident, theapparatus is effective and efficient in operation, since cooling of allparts of the material is substantially uniform for various rates offlow, and the apparatus also may be operated to achieve substantiallyuniform cooling when the flow is periodic, as in the case of sugar in asugar factory, when the flow is heavy immediately succeeding a white panstrike, and diminishes thereafter, but again becomes heavy when anotherwhite pan is struck.

Although a specific embodiment of this invention has been described withparticularity, and certain possible variations therein indicated, itwill be understood that other variations may be made, and that other anddifferent embodiments of this invention may exist, all without departingfrom the spirit and scope thereof.

What is claimed is:

1. Heat transfer apparatus for granular material, comprising a shelldefining a space for a heat transfer fluid; means for supplying suchheat transfer fluid to said space adjacent one end of said shell and forremoving such heat transfer fluid from said space adjacent the oppositeend of said shell; a first plurality of tubes extending through saidspace in sealed relation thereto and disposed generally vertically; aninner tube disposed within each of said first tubes and having aconnection with said space adjacent the upper and lower ends of saidfirst tube, said inner tubes being sealed with respect to the interiorof said first tubes; and an inverted cone at the lower end of each ofsaid first tubes for restricting the flow of granular material, eachsaid inverted cone having sides disposed at an angle to the horizontalgreater than the angle of repose of said granular material, each saidcone being provided at its lower end with a discharge orifice having across sectional area less than the cross sectional area of the granularmaterial space between said first tube and said inner tube therein andthereby restricting the downward descent of granular material throughthe corresponding tube to less than free fall so as to maintain granularmaterial in contact with said tube during such descent.

2. Apparatus for cooling granular material such as sugar, comprising anupright cylindrical shell; upper and lower tube sheets having aplurality of circular apertures and closing the respective ends of saidshell; a plurality of first tubes disposed generally within a hexagonand registering with said apertures, said tubes extending between saidtube sheets and sealed thereto at said apertures; a cylindrical innertube disposed within each of said first tubes and extending inconcentric relation thereto, each said inner tube having a plurality ofsets of laterally extending rods, said sets being disposed in spacedvertical relation and said rods maintaining said inner tube inconcentric relation to said first tube, each said inner tube having aninlet liquid connection adjacent the bottom of said first tube and aliquid outlet connection adjacent the top of said first tube, each ofsaid connections facing outwardly toward said shell; an inverted conicalflow control device having side walls forming an included angle ofsubstantially 60 and provided at the lower end with a circular orificehaving a cross sectional area less than the cross sectional area of theannular space between an inner tube and a first tube, each said invertedconical flow control device being attached to the underside of saidlower tube sheet in substantially axial alignment with a first tube;means for supplying cooling water to the space within the periphery ofsaid shell adjacent the lower end thereof; means for removing water fromthe space within said shell adjacent the upper end thereof; and a seriesof horizontal baffles disposed in spaced vertical relation within saidshell, each bafile having a series of circular apertures thereindisposed substantially concentrically with respect to said first tubesand through which said first tubes extend, the annular cross sectionalarea formed by said apertures around each of said first tubes being lessthan the area of the inner tube therewithin.

3. Apparatus for cooling granular material such as sugar, comprising anupright cylindrical shell; upper and lower tube sheets having aplurality of circular apertures disposed generally Within a hexagon andclosing the respective ends of said shell; a plurality of first tubesregistering with said apertures, said tubes extending between said tubesheets and sealed thereto at said apertures; an outlet housing connectedto the lower end of said shell having an inverted conical form and anoutlet opening at the bottom; an outlet valve below said outlet housing;a discharge pipe leading from said valve and provided with a flowcontrol orifice; an inlet housing connected to the upper end of saidshell and having sides forming a hexagon at said upper tube sheet; acylindrical inner tube disposed within each of said first tubes andextending in concentric relation thereto, each said inner tube having aplurality of sets of laterally extending rods, said sets being disposedin spaced vertical relation and said rods maintaining said inner tube inconcentric relation to said first tube, each said inner tube having aninlet liquid connection adjacent the bottom of said first tube and aliquid outlet connection adjacent the top of said first tube, each ofsaid connections facing outwardly toward said shell; an inverted conicalflow control device having side walls forming an included angle ofsubstantially 60 and provided at the lower end with a circular orificehaving a cross sectional area less than the cross sectional area of theannular space between an inner tube and a first tube, each said invertedconical flow control device being attached to the underside of saidlower tube sheet in substantially axial alignment with a first tube; ahorizontal series of water inlet holes spaced about the periphery ofsaid shell adjacent the lower end thereof; a water inlet manifoldencircling said shell and enclosing said inlet holes; a horizontallydisposed series of water outlet holes in said shell adjacent the upperend thereof; a horizontally disposed water outlet manifold surroundingsaid shell and enclosing said outlet holes; a hexagonal inlet platemounted on said upper tube sheet and having a series of spaced circularapertures registering with said first tubes, said first tubes beingdisposed generally within a hexagon, said inlet plate having surfacesextending upwardly and outwardly away from each said aperture at anangle of approximately 60 to the horizontal, the thickness of said inletplate being such that the sloping surfaces from adjacent aperturesintersect in pointed ridges; a series of horizontal bafiles disposed inspaced vertical relation within said shell, each bafiie having a seriesof circular apertures therein disposed substantially concentrically withrespect to said first tubes and through which said first tubes extend,the annular cross sectional area formed by said apertures around each ofsaid first tubes being less than the area of the inner tube therewithin;and means in said upper housing for determining the extent of a pile ofgranular material filling said first tubes and extending upwardly withinsaid inlet housing.

4. Apparatus for cooling granular material such as sugar, comprising anupright cylindrical shell; upper and lower tube sheets having aplurality of circular apertures and closing the respective ends of afluid space within said shell; a plurality of first cylindrical tubesregistering with said apertures, said tubes extending between said tubesheets and sealed thereto at said apertures; a cylindrical inner tubedisposed within each of said first tubes and extending in concentricrelation thereto, each said inner tube having an inlet liquid connectionadjacent the bottom of said first tube and a liquid outlet connection adacent the top of said first tube; an inverted conical flow controldevice for each said first tube and provided at the lower end with acircular orifice having a cross sectional area less than the crosssectional area of the annular space between the corresponding inner tubeand first tube, each said inverted conical flow control device beingattached to the underside of said lower tube sheet in substantiallyaxial alignment with a first tube; means for supplying cooling water tothe fluid space within said shell adjacent the lower end thereof; andmeans for removing water from the fluid space within said shell adjacentthe upper end thereof.

5. Apparatus for cooling granular materials such as sugar, as defined inclaim 4, including a series of horizontal baflles disposed in spacedvertical relation Within said shell, each bafiie having a series ofcircular apertures therein disposed substantially concentrically withrespect to said first tubes and through which said first tubes extend,the annular cross sectional area formed by said aperture around each ofsaid first tubes being less than the cross sectional area of the innertube therewithin.

6. Apparatus for cooling granular material, as defined in claim 4,including an inlet plate above said upper tube sheet and havingapertures registering with the apertures of said upper tube sheet, saidinlet plate having surfaces leading to each said tube sheet aperture,inclined at an angle to the horizontal greater than the angle of reposeof said granular material, said inlet plate having sufiicient thicknessthat the surfaces between adjacent apertures intersect in ridges.

References Cited in the file of this patent UNITED STATES PATENTS

1. HEAT TRANSFER APPARATUS FOR GRANULAR MATERIAL, COMPRISING A SHELLDEFINING A SPACE FOR A HEAT TRANSFER FLUID; MEANS FOR SUPPLYING SUCHHEAT TRANSFER FLUID TO SAID SPACE ADJACENT ONE END OF SAID SHELL AND FORREMOVING SUCH HEAT TRANSFER FLUID FROM SAID SPACE ADJACENT THE OPPOSITEEND OF SAID SHELL; A FIRST PLURALITY OF TUBES EXTENDING THROUGH SAIDSPACE IN SEALED RELATION THERETO AND DISPOSED GENERALLY VERTICALLY; ANINNER TUBE DISPOSED WITHIN EACH OF SAID FIRST TUBES AND HAVING ACONNECTION WITH SAID SPACE ADJACENT THE UPPER AND LOWER ENDS OF SAIDFIRST TUBE, SAID INNER TUBES BEING SEALED WITH RESPECT TO THE INTERIOROF SAID FIRST TUBES; AND AN INVERTED CONE AT THE LOWER END OF EACH OFSAID FIRST TUBES FOR RESTRICTING THE FLOW OF GRANULAR MATERIAL, EACHSAID INVERTED CONE HAVING SIDES DISPOSED AT AN ANGLE TO THE HORIZONTALGREATER THAN THE ANGLE OF REPOSE OF SAID GRANULAR MATERIAL, EACH SAIDCONE BEING PROVIDED AT ITS LOWER END WITH A DISCHARGE ORIFICE HAVING ACROSS SECTIONAL AREA LESS THAN THE CROSS SECTIONAL AREA OF THE GRANULARMATERIAL SPACE BETWEEN SAID FIRST TUBE AND SAID INNER TUBE THEREIN ANDTHEREBY RESTRICTING THE DOWNWARD DESCENT OF GRANULAR MATERIAL THROUGHTHE CORRESPONDING TUBE TO LESS THAN FREE FALL SO AS TO MAINTAIN GRANULARMATERIAL IN CONTACT WITH SAID TUBE DURING SUCH DESCENT.